It's in the way Sora looks so surprised to see him that makes Riku decide to do it. He shoves a chest over the trapdoor so that those stupid animals won't interrupt, and then it's just him, Sora, and a Kairi that won't wake up in the captain's cabin. Yeah, Sora's eyes are big and wide and just as blue as they've always been. And he looks kind of confused, like he hasn't remembered that he's supposed to be angry with Riku yet, so he'd better take advantage of the situation while it lasts.
"Sora," he says, smilesmirking as he lightly pushes the brunet against the wooden bulkhead, reminding himself that he's confident it's going to work.
"...Riku?" So he's still confused. But he's not objecting, so that's a good sign. And he's biting his lip like he doesn't know what he should do, but just keeps looking up at him like maybe Riku will explain it.
"I wanted you to beat the ones below-deck," he answers, lowers his voice a little like it's a secret. "You're too good to lose a fight to little ones like those." And Sora leans towards him a little, too, either to hear him better... or, maybe, just because he wants to. Yeah, Riku likes the sound of that.
"Then why did you-" He puts a hand to Sora's mouth and watches the other boy's eyes widen just that extra bit more. His lips are so soft, and Riku wonders what they'd feel like if it wasn't just his hand against them.
"You don't need to bother with them, Sora, they're way under your level," he explains, still smiling. Sora looks like he needs a little bit more clarification, though, and doesn't interrupt again when Riku removes his hand and leans in a bit himself. "You should learn to go for the things that really matter." And it's then that Riku cements his decision and eliminates the gap between his and Sora's mouths.
Sora's shocked, at first, and is mostly unmoving in his surprise, but Riku is resolute in pushing his advantage, and it's only a few moments more until Sora relaxes into it. The brunet is tentative still, like he's only just now starting to get what's going on, but it's worth the little gasp he makes when Riku lets his tongue move across the crease of Sora's lips. And because Sora's lips are parted a little, now, his tongue doesn't hesitate in starting its first exploration of the inside of Sora's mouth. For a dizzying minute or two, it’s just them; they're the only two people that're on this entire world, but it's over far too soon.
"Come on, Sora," he says, after they've broken apart for air, "We don't have to fight each other. We can help her together." And he's a fifteen-year-old boy, and using the Darkness always makes him a little horny, and Sora is right here and still hasn't given an indication that he wants to be anywhere else. He drinks it all in, the way Sora's breathing, the way his cheeks are pink, the way his mouth is still a little bit open. And Sora's eyes look so huge when they're this close, miles-deep blue and hanging on his every word... come on, Sora.
Or maybe he just needs more encouragement? So he kisses Sora again, a deeper one this time, and Sora makes a muffled little noise into his mouth when Riku lets his tongue dip in more confidently than the first time. And that hand that isn't holding Sora's shoulder against the bulkhead comes to rest on Sora's waist, slides down to the outside of his thigh. He's not gripping onto Sora too hard, just decisive enough to make a point, but not so forcefully that Sora couldn't push him away if he really wanted to. And because Sora isn't pushing him away, Riku lets the hand on Sora's thigh slowly make its way to a more central location.
"It'll be just us, Sora," he breathes, after they're parted again, lips just inches from Sora's, "just like old times." He doesn't mention that his hand pressing against the front of Sora's shorts isn't like anything they've ever done before, but it's the thought that counts, right? And yeah, the way that Sora can't stop his hips from pushing back, that's getting somewhere.
"But the Heartless-" Somehow, even after all that, Sora's starting to remember why he was mad at Riku before, so he has to stop that. He pushes with his hand again, and Sora’s breath hitches.
"-do what I tell them to do." Sora shakes his head like he's trying to clear cobwebs out of it, and moves Riku's hand away from him with a small downturn in his mouth. Riku thinks he kind of likes Sora's mouth better when he's doing things other than talking and messing things up.
"They're monsters, Riku. And what about Donald and Goofy?" Sora just won’t stop going on about what he thinks Riku should and shouldn’t do; doesn’t he know that Riku’s actions up to this point are what helped him find Kairi in the first place? And god, not those stupid animals again. Riku resists the urge to clench his teeth.
"You don't need them, Sora. They're not going to care about what happens to Kairi, are they? They just care about their mission, right?" But Sora won't stop frowning, and this time he does push Riku back, not roughly, but again, decisive.
"Not with the Heartless. And not without Donald and Goofy." A weight drops into Riku's stomach like a ball of ice.
"You'd really choose them over the friends you've known your whole life?" Over me, he wants to say, but doesn't. He steps back further, until he's standing in front of where Kairi's laying in her strange, unaware state. Her arm's fallen off the bunk, like her hand's been reaching towards the boys, but he knows that it's just the motion of the ship doing that. Kairi never moves by herself anymore.
"That's not it, Riku! If you'd just listen-" And he's got this frustrated face on now, like Riku's the one who's being difficult.
"I think I've heard enough," he responds coldly, and bends to pick Kairi up before facing Sora once more. Another tug at his Darkness, and Sora's shadow rises up from the floorboards. Oh, it looks like that stung. Good. "Have fun, Sora." And Riku takes a step back, towards Hollow Bastion.